Heating Units and Controls
There are four common types of heating
- A furnace provides heat through a forced
air distribution system.
- A boiler provides heat through a hydronic
distribution system. (Hydronic systems are also
referred to as hot water systems.)
- A space heater supplies heat directly to the
room where it is located.
- A heat pump extracts heat from the air, ground
or water outside the house and usually delivers
it through a forced air distribution
Most heating systems need air for combustion.
Furnaces, boilers and space heaters that burn fuels need a supply of air to be
able to burn properly, and a vent to the outdoors so that combustion gases can
escape from the house. Electric heaters do not need to be vented. Combustion is
a two-step process: air in, and gases out.
In the past, there was usually plenty of air
leaking into a house to keep the furnace, boiler or stove burning well. Modern
homes, however, are better sealed and use controlled ventilation, rather than
uncontrolled leakage, to provide greater comfort and energy efficiency. Vents
that supply air for heating units should never be blocked. It is important to
ensure that there is an adequate supply of combustion air available, even when
other air exhausting equipment is in use.
Venting used to be done through a chimney. Today,
however, many models of natural gas, oil and propane equipment can be vented by
pipe directly through the wall, which greatly simplifies
installation. Remember that combustion gases cannot
escape from your home unless you provide air to replace them. That’s why venting
problems can often be traced to air supply problems.
The indoor temperature is automatically controlled
by a thermostat. Two important considerations are location and type. Central
systems are normally controlled by a single thermostat. To achieve proper
temperature control, the thermostat must be located in an area where it will
sense the “average” indoor temperature. Locations exposed to
localized temperature extremes
(outside walls, drafts, sunlight, hot ducts or pipes,
etc.) should be avoided.
Different types of thermostats are available. Basic
types maintain a fixed indoor temperature. However, you can reduce your heating
costs by installing a set-back thermostat which can be programmed to
automatically lower the temperature when no one is home or everyone is in bed,
and then warm up the house before you get home or wake up. Savings will vary,
but a set-back of 3ºC for eight hours daily could reduce your heating costs by
Where space heaters are used, each unit will likely
be individually controlled by its own thermostat – which is usually the basic
type. This allows you to keep unused areas at a lower temperature than those
areas you do use.
There are three types of distribution
- A forced air system circulates warmed or cooled air
around the house through a network of ducts. It also provides a means of
distributing ventilation air.
- A hot water (hydronic) system distributes heat
through hot water pipes and radiators.
- Space heaters, though not technically a distribution
system, provide direct heat to the room in which
they are located.
It is important that a distribution system is
properly designed, installed and operated to ensure maximum energy efficiency
and comfort levels. Try to avoid placing any part of your distribution system
outside of your home’s insulation. This is sometimes done as a simple remedy to
a routing problem, but there is always some heat loss through the wall of any
distribution system. It is better that any losses heat (or cool) you rather than
Registers in each room can be adjusted to control
the air flow. Return registers draw air from the rooms through separate ducts
back to the furnace to complete the cycle of air flow through the
house. Leaks in forced air distribution systems are
often ignored because they normally do not cause any obvious damage, but it is
important to avoid/eliminate such leaks. Leaks will affect a distribution
system’s ability to provide comfort in all areas of the house, and leaks in some
parts of the system can result in significant energy loss and/or
condensation-related damage which may be hidden from sight.
Hot water (Hydronic)
Distributes hot water from a boiler to radiators,
convectors or under-floor heating systems in each room. In older homes, large
cast-iron radiators are common. Modern systems feature smaller boilers, narrow
piping and compact radiators that can be regulated to provide temperature
control in each room. Under-the-floor heating systems can be built into the
floors of new and existing homes.
These have no central heating unit or distribution
system. Instead, individual space heaters – such as a wood stove, electric
baseboards, radiant heaters or heaters fueled with oil, natural gas or propane –
supply heat directly to the room. For safety, all space heaters except electric
ones need to be vented to the outside. An appropriately sized space heater can
supply some heat to all parts of a home if the design of the home allows for
natural distribution of heat from the heater location. In most cases, more than
one unit is required to comply with building code requirements, but multiple
units allow you to vary the temperature around the house.